Plant Immunity Research Center, Seoul National University, Seoul 08826, Korea.
Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 08826, Korea.
Mol Plant Microbe Interact. 2024 Apr;37(4):370-379. doi: 10.1094/MPMI-09-23-0145-R. Epub 2024 Apr 19.
bacteria use secreted apoplastic effectors, such as putative serine proteases, for virulence in host plants and for hypersensitive response (HR) induction in nonhost plants. Previously, we have shown that ChpG is important for the necrosis development in pepper () leaves. Here, we determine the function of ChpG, along with three paralogous proteins, for HR induction in the apoplastic space of a nonhost plant, . The full-length and signal peptide-deleted (ΔSP) mature forms of all proteins fused with the tobacco PR1b signal sequence were generated. The full-length and ΔSP forms of ChpG and only the ΔSP forms of ChpE and Pat-1, but none of the ChpC, triggered HR. Based on the predicted protein structures, ChpG carries amino acids for a catalytic triad and a disulfide bridge in positions like Pat-1. Substituting these amino acids of ChpG with alanine abolished or reduced HR-inducing activity. To determine whether these residues are important for necrosis development in pepper, alanine-substituted genes were transformed into the . PF008ΔpCM1 strain, which lacks the intact gene. The strain with any variants failed to restore the necrosis-causing ability. These results suggest that ChpG has a dual function as a virulence factor in host plants and an HR elicitor in nonhost plants. Based on our findings and previous results, we propose apoplastic effectors, such as ChpG, Pat-1, Chp-7, and ChpG, as hypersensitive response and virulence (Hrv) proteins that display phenotypic similarities to the hypersensitive response and pathogenicity (Hrp) proteins found in gram-negative bacteria. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.
细菌利用分泌的质外体效应子，如假定的丝氨酸蛋白酶，在宿主植物中发挥毒性作用，并在非宿主植物中诱导过敏反应（HR）。此前，我们已经表明 ChpG 对辣椒叶片坏死的发展很重要。在这里，我们确定了 ChpG 以及三个同源蛋白在非宿主植物质外体中诱导 HR 的功能。所有蛋白的全长和信号肽缺失（ΔSP）成熟形式都与烟草 PR1b 信号序列融合。全长和ΔSP 形式的 ChpG 以及仅ΔSP 形式的 ChpE 和 Pat-1，但 ChpC 的任何形式都没有触发 HR。根据预测的蛋白质结构，ChpG 携带位于 Pat-1 类似位置的催化三联体和二硫键的氨基酸。用丙氨酸取代 ChpG 的这些氨基酸会破坏或降低 HR 诱导活性。为了确定这些残基是否对辣椒坏死的发展很重要，将突变的基因转化到缺乏完整基因的中。携带任何变体的菌株都无法恢复引起坏死的能力。这些结果表明 ChpG 具有作为宿主植物毒力因子和非宿主植物 HR 诱导剂的双重功能。基于我们的发现和以前的结果，我们提出了质外体效应子，如 ChpG、Pat-1、Chp-7 和 ChpG，作为过敏反应和毒性（Hrv）蛋白，它们与革兰氏阴性细菌中的过敏反应和致病性（Hrp）蛋白表现出相似的表型。[公式：见正文]版权所有 © 2024 作者。这是一个在 CC BY-NC-ND 4.0 国际许可下发布的开放获取文章。
